In looking more at the Internet I made a discovery . . . apparently my radio does switch from 9 to 10 khz tuning spacing, but if you tune slow it will tune 1khz at a time set either way, if you tune fast it skips 9 or 10 khz per the way it is set . . . the problem is trying to get the tuning knob rotating speed right so it skips 9 or 10 khz per the way it is set.
I never knew this, here it is from a review of the radio on the Internet,
Something to get used to is the way Tecsun implemented manual tuning. When you rotate the tuning knob fast, the radio will skip frequencies by the standard channel spacing (e.g. 9 KHz on MW, 5 KHz on SW). When rotating slowly, the radio will tune one KHz at the time. It proved to be very challenging to get the rotation speed just right.
So, my radio does tune 10 khz steps, but what an odd way to do it.
Al
If it's like the PL-398, really you have fast tuning -- where the tuning goes up 2, 3, 4, 8, 12, whatever kHz, and and 'slow' tuning, i.e. 1 kHz steps. This goes for MW as well as SW. There really is no 5 or 10, or 9 kHz tuning like many radios have.
On my PL-398, the only thing the 9 kHz/10 kHz switching does is
change the thermometer to degrees C when it's on 9 kHz setting, instead of
degrees F when it's in 10 kHz setting. That's it. There really is no difference in how the tuner operates. Direct entry of MW frequencies may or may not be affected. I haven't tried to see if, when in "9 kHz spacing", the direct entry of a 9 kHz frequency works correctly or not. My guess it that the radio doesn't really care, and that may be the same way with your PL-310.
It's just one of those fun things you get used to. My PL-398 otherwise is a great radio for SW, good for MW, great for FM, and there's nothing around here to hear on LW but it works....